Slide fastener stringer



July 21, 1964 L JONES ETAL 3,141,217

SLIDE FASTENER STRINGER Filed July 25, 1961 3 Sheets-Sheet l 3 I I i a Q A. L. JONES ETAL SLIDE FASTENER STRINGER July 21, 1964 Filed July 25. 1961 3 Sheets-Sheet 2 y 21, 1964 A. L. JONES ETAL 3,141,217

SLIDE FASTENER STRINGER Filed July 25, 1961 3 Sheets-Sheet 3 c A FIG.4

l L l United States Patent 3,141,217 SLIDE FASTENERSTRINGER Arthur Llewelyn Jones and Eric Engel Cnckson, both of Penrith, New South Wales, Australia, assignors to W. E. Cuckson & Son Proprietary Limited, St. Marys, New South Wales, Australia, a corporation of New South Wales Filed July 25, 1961, Ser. No. 134,063 6 Claims. (Cl. 242 ll5.1)

This invention relates to improved constructions of stringers for sliding clasp fasteners, and to fasteners incorporating the same.

In recent times some advancement has been made in the simplification of sliding clasp fastener construction. The trend has been towards the substitution of thermoplastic tapes for the previously conventional metal interlocking elements. One exemplary construction involves the use of two lengths of identical thermoplastic tapes with the interlocking elements extruded on each as laterally extending recessed teeth. These tapes may be welded or stitched directly to the fabric of the garment or to a ribbon of fabric which subsequently is attached to. the garment.

Although this latest type of sliding clasp fastener is considerably more economical to produce, a design has not yet been evolved Which will satisfactorily withstand a truly acceptable degree of separation forces. More particularly is transverse separation likely to occur when the stringers are folded back upon themselves about a small radius with the interlocking elements outermost. Such a condition has been found normally to result in a spreading apart of the mating elements whereby a relatively small transverse force will effect separation of the stringers.

The prime object of the invention is to provide thermoplastic tapes for the stringers of sliding clasp fasteners which are capable of withstanding comparatively large separation forces even under abnormal conditions of use.

Another object is to provide such tapes whose functioning efficiency remains substantially unchanged should the fabric to which they are attached shrink after washing.

The invention can be expressed generally as providing a stringer for a sliding clasp fastener composed of a strip of flexible tape with transverse interlocking elements formed on the tape, and being characterized in that the two longitudinal edges of the tape are of dissimilar lengths with the relative difference in lengths dispersed substantially uniformly over most of the length of the tape.

A feature of the invention is that stringers with this construction are of the type in Which each interlocking element has a head and is spaced from adjacent elements to leave a recess between each pair of interlocking elements with at least part of the recess. overlying the tape and at least a portion of the head extending laterally past the edge of the tape, whereby when the stringer is mated with a corresponding stringer, each. head is. received in an opposed recess with the extending portion overlying the mating tape and held in position against displacement in two directions.

According to another feature each stringer has a re. inforcing cord extending longitudinally thereof beneath the interlocking elements and adjacent the inner side of the tape.

Furthermore, it is also a feature of the ivention that the strip of tape of each stringer is affixed to a fabric ribbon which is in a longitudinally crimped condition to. compensate for subsequent shrinkage of the warp threads therein and to avoid separation of the fastenerunder some conditions of use.

The interlocking elements of this invention are formed 3,141,217 Patented July 21, 1964 integrally with the tape and both are of thermoplastic material and may be produced by any convenient process, such as cast in moulds or extruded and then rolled. For convenience of description throughout this specification a tape and its interlocking elements is referred to as a stringer although in many instances the tape willbe in turn secured to a textile ribbon.

The invention, and the manner of carrying the same into effect, will be more fully explained with reference to the accompanying drawings in which:

FIG. 1 shows in perspective a pair of interlocked stringers constructed according to the present invention, each of said stringers being welded to a fabric ribbon, this view showing the stringers remaining. interlocked when the fabric is folded back on itself over a curve of small radius;

FIGS. 2 and 3 show in perspective a View from one side of the stringers and an inverted view, respectively, in which the stringers each have a reinforcing cord extending longitudinally of the tapes and being enclosed therein;

FIG. 4 shows on a greatly enlarged scale the longitudinal compacted condition of the fabric ribbon asthe stringer is secured thereto, FIG. 4A is a longitudinal sectional view takenthrough the ribbon and stringer of FIG. 4 showing the ribbon in crimped condition and FIG. 4b is a sectional view through the ribbon at a location further to the right in FIG. 4.

The figures show a sliding clasp fastener 4 which consists of a pair of mating stringers 5, and. 6 composed of tapes 7 and 8 and spaced interlocking elements 9 and 10 respectively. In use a conventional type of slider (not shown) is used to effect fastening or separation. of the stringers 5 and 6. Each tape 7 or 8 is formed from a thermoplastic material and has its associated elements 9 or 16 integrally formed thereon.

As shown, the interlocking elements 9. and. 10 are formed on one side of their respective tapes 7 and 8 as longitudinally spaced transversely. extending elements having in plan a rectangular base 11 and a head 12 interconnected by a narrow stem 13-. The side walls 14 of the elements 9 and 10 may be upright with respect to the tapes 7 and 8. The heads 12 of the elements 9 and 10 in the embodiment depicted in. the drawings each have a chamfered edge 9a.on their underside beyond the longitudinal edge 7a of the tape. The width of the head 12 is greater than the width of the stem 13. so as to form abutment shoulders 15 and a recess 16 betweeneachhead 12. and the base 11, the recesses 16. being so shaped as to accommodate the heads. of the elements on amating stringer. When the tapes 7 and 8 are fastened together the shoulders 15 of adjacent interlockingelements 9 and 10 are in contact as shown in FIGS. 2 and 3. The shoulders 15 instead of being at right angles to the walls of the stems. 13 are at a slightly greater angle, for example about to such walls. The corners 1-7 of each head 12: can, if desired, be radiused to reduce wear during use.

The interlocking elements 9 and 10 are positioned with respect to their tapes 7 and 8 so that their bases 11 are spaced from the respective inner longitudinal edge 7a or 8a of the tape, the greater part of the recesses 16 overlies their respective tapes and the head portion 12 extends laterally of the tape.

With this arrangement two stringers may be fastened securely together by forcing them together at an inclined angle to each other in the same manner as is done with the conventional metal elements. Due to the resiliency of the thermoplastic material as well as the angular dis placement of the stringers 5 and 6, each head portion 12 may be made to enter into the recesses 16 between adjacent heads 12 of the elements in the corresponding position on the mating tape. The tapes 7 and 8 are fastened together with the shoulders 15 of engaging interlocking elements 9 and 10 in contact. The fastening of the stringers 5 and 6 in this way provides a secure joint against normal transverse separation forces as well as against forces acting in a plane at right angles to the plane of the stringers. The safeguard against separation by these latter forces is provided by the feature of extending the heads 12 laterally of their tapes 7 or 8 so that when the stringers are fastened together the heads 12 (or at least a portion of them) overlie the tape of a respective mating stringer 5 or 6. The obstruction provided by the mating tapes overlying the heads 12 of the interlocking elements prevents the heads 12 from being displaced from their recesses 16 in a generally vertical direction to the plane of the tape.

The conventional skirt 21 of the slider 22 (see FIG. 3) engages the outer wall of the bases 11 to hold the stringers against transverse separation at the fastening point 23. The stringers of this invention furthermore embody means to prevent transverse separation of the interlocking ele ments 9 and 10 under abnormal conditions of use such as when two such mated stringers are folded back upon themselves in a curve of small radius the inside of which is on the side of the tape remote from the interlocking elements, is. the latter elements are outermost. Such means are provided by forming the stringers 5 and 6 in a particular manner, and if desired by additionally providing one or more substantially inextensible textile threads extending longitudinally through the tapes and transversely of the bases 11 of the interlocking elements 9 and 10.

In accordance with a preferred form of the present invention the stringers are cast, moulded or extruded around a conical surface with the inner longitudinal edge or 8a of the tape formed on a surface of smaller diameter than the outer longitudinal edge 711 or 8b of the tape. The edge 7a or 8a will, therefore, be shorter than the tape. The edge 7a or 8a will, therefore, be longer than the other lateral edge. Regardless of whatever forming process is used the thermoplastic material of the stringers will be allowed to solidify (or at least partly so) upon a surface which will produce dissimilar lengths of the two lateral edges of the tape with the relative difference in length dispersed substantially uniformly over most of the length of the tape. It has been found that when a stringer made in this manner is folded over a small radius compressive stresses will result which tend to move the heads 12 of the interlocking elements at the fold inwardly along the radius of the fold. Thus when two such stringers are mated to form a fastener these stresses will result in the fastener remaining interlocked when bent over in a tight fold. With stringers made in this way it has been found advisable for the shoulders 15 of the interlocking elements to be obliquely shaped as previously described, i.e. they should be at an angle of slightly more than 90, for example 105, with respect to the walls of the stems 13 in order to facilitate the action of such stresses in an interlocked fastener. The angle of the conical surface on which the stringers may be moulded will vary somewhat according to the type of thermoplastic material being used. With many of the nylon materials an angle of between about 5 to 10 has been found suitable. A smaller angle than this could be used with materials possessing a greater tensile and C0111- pressive strength than nylon, and conversely materials of lesser strength than nylon would require the employment of a larger angle.

, One or more textile or like threads 18 extending transversely beneath the bases of the interlocking elements and thus longitudinally of the stringers may be provided as shown in the drawings. Stringers 5 and 6 having one such thread 18 are shown in FIGS. 2 and 3. Threads of cotton or linen have been found to possess adequate strength and be suitably non-extensible and are thus suitable for use in the stringers of this invention. The thread, or threads 18, may be attached to the tapes 7 and 8 after the stringer has been formed by means of an adhesive or the like. However, it is preferred to incorporate the threads within the tape of the stringer during the forming operation as this results in a stronger and more durable stringer wherein more intimate frictional contact is made between the thread 18 and its tape. It is further preferred to place such thread or threads 18 so that they pass as near as possible beneath the center of the length of the fastener elements 9 and 10. In use a stringer having one or more continuous threads 18 extending through its tape will serve to restrain the spreading apart of interlocking elements when the fastener is folded. When such a fastener is folded upon itself the thread or threads 18 will act as a tensioning thread, thereby transmitting compressive forces to the interlocking elements 9 and 10 which will tend to move the heads 12 of these elements inwardly along the radius of the fold.

The stringers 5 and 6 of this invention being made of a thermoplastic material can be fusion welded to textile ribbons 19 (i.e., ribbons manufactured as narrow woven tapes) in which condition they will normally be offered for sale for subsequent sewing to a garment. Alternatively, the strips of flexible tapes 7 and 8 carrying the integral interlocking elements can be made of sufiicient width to permit welding of the stringers 5 and 6 directly to the garments on which they are to be used.

Another factor which may lead to an ineflicient operation with normal use is shrinkage of the textile ribbon 19. To avoid this effect the textile ribbon 19 when attached to the stringer 5 or 6 is not under any tensile stress but is in a crimped condition. This is achieved by forcibly feeding the textile ribbon 19 at a faster rate than the joining point with the thermoplastic stringer. If provision is also made to keep the ribbon flat, a compacting together of theweft threads results with a consequential slackening of the warps, which in the ideal case become more Wavy in form. This longitudinal compacting of the ribbon will be retained on the side of the ribbon to which the stringer is fusion welded. It is preferred to have the textile ribbon 19 crimped, as shown in FIG. 4, an amount of approximately 5 to 10% of the length of the ribbon 19. This means that the ribbon 19 towards the centre 20 of the fastener is approximately 5 to 10% compressed in length thereby leaving the outer edge of the ribbon in a finished fastener longer than the edge at the center 20. A similar procedure to this should also be adopted where the stringers 5 and 6 are to be attached directly to the garment on which they are to be used. It has been found that slide fasteners assembled in accordance with the above procedure, particularly those wherein the stringers 5 and 6 have one or more continuous textile threads 18 extending through them, will remain functionally eflicient after washing as this arrangement will compensate for shrinkage of the textile ribbon 19 and thus avoid crimping or curving of the fastener occurring.

Principally, however, the value of pre-crimping the textile ribbon 19 will be found to be the resultant protection obtained against undesired separation of the stringers 5 and 6 under some abnormal conditions of use. For instance should the interlocked stringers 5 and 6 be folded back upon themselves with the interlocking elements 9 and 10 innermost, most of those separation stresses are avoided which would otherwise result due to the tightness of the fabric ribbon 19 at the fold.

What we claim is:

1. A support for a sliding clasp fastener constituted by a pair of stringers each comprising a strip of flexible tape, transverse interlocking elements of the same material as said tape and integral with said tape, said transverse interlocking elements extending from at least one face of the tape, each element including a head and being spaced from adjacent of the said elements to leave a recess between each pair of interlocking elements with at least part of the recess overlying the tape and at least a portion of the head extending laterally past a longitudinal edge of the tape, whereby When said stringer is mated with a corresponding stringer, each head being received in an opposed recess with the extending portion overlying the mating tape and held in position against displacement in two directions, and a substantially fixed-length, reinforcing cord embedded in said tape beneath the interlocking elements, extending longitudinally through said tape adjacent the said edge, each head having a charnfered surface beyond said edge of the tape, the tape being of thermoplastic material and having said edge of the tape longer than the opposite longitudinal edge with the relative difference in lengths between the two edges dispersed uniformly over the length of the tape, said stringers being assembled to form said support with shorter edges of the stringers in confronting relation.

2. A stringer for a sliding clasp fastener as claimed in claim 1, wherein each said interlocking element includes a base portion, a tapering head, and a stem narrower than both the base portion and the head interconnecting the base and the widest part, each head including ends projecting beyond the stern and forming oblique abutment shoulders adjacent the stem.

3. A sliding clasp fastener comprising a pair of mating stringers, each stringer having a strip of flexible tape, a textile ribbon secured in a longitudinally crimped condition in substantially wavy form to each tape of the stringers, transverse interlocking elements of the same material as said tapes and integral with each said tape, said transverse interlocking elements extending from one face of each of said tapes, a substantially fixed-length reinforcing cord embedded in said tape beneath the interlocking elements extending longitudinally through each said tape, each said tape having an outer longitudinal edge longer than its inner longitudinal edge with the relative difference in lengths between the two edges dispersed uniformly over the length of the tape and with the shorter edges of the tapes in confronting relation, and a slider engageable with said stringer for moving said tapes toward and away from each other to interlock and separate said elements of one tape with respect to said elements on the mating tape.

4. A sliding clasp fastener according to claim 3, wherein each said interlocking element includes a head and is spaced from adjacent elements to leave a recess between each pair of interlocking elements with at least part of the recess overlying the tape and at least a portion of the head extending laterally past said inner edge of the tape, and said extending portion of the head has a chamfered surface.

5. In a sliding clasp fastener, the combination of a stringer constituted by a strip of flexible tape, transverse interlocking elements of the same material as said tape and integral With said tape, said transverse interlocking elements extending from one face of said tape, and a textile ribbon secured in a longitudinally crimped condition and in substantially wavy form to said tape.

6. In a sliding clasp fastener the combination as claimed in claim 5, wherein said textile ribbon is crimped 5% to 10% in length before being secured to said tape.

References Cited in the file of this patent UNITED STATES PATENTS 2,525,284 Camp Oct. 10, 1950 2,744,313 Warburton May 8, 1956 2,796,649 Soave June 25, 1957 2,873,501 Renner Feb. 17, 1959 3,003,212 Emery Oct. 10, 1961 FOREIGN PATENTS 681,941 Great Britain Oct. 29, 1952 

1. A SUPPORT FOR A SLIDING CLASP FASTENER CONSTITUTED BY A PAIR OF STRINGERS EACH COMPRISING A STRIP OF FLEXIBLE TAPE, TRANSVERSE INTERLOCKING ELEMENTS OF THE SAME MATERIAL AS SAID TAPE AND INTEGRAL WITH SAID TAPE, SAID TRANSVERSE INTERLOCKING ELEMENTS EXTENDING FROM AT LEAST ONE FACE OF THE TAPE, EACH ELEMENT INCLUDING A HEAD AND BEING SPACED FROM ADJACENT OF THE SAID ELEMENTS TO LEAVE A RECESS BETWEEN EACH PAIR OF INTERLOCKING ELEMENTS WITH AT LEAST PART OF THE RECESS OVERLYING THE TAPE AND AT LEAST A PORTION OF THE HEAD EXTENDING LATERALLY PAST A LONGITUDINAL EDGE OF THE TAPE, WHEREBY WHEN SAID STRINGER IS MATED WITH A CORRESPONDING STRINGER, EACH HEAD BEING RECEIVED IN AN OPPOSED RECESS WITH THE EXTENDING PORTION OVERLYING THE MATING TAPE AND HELD IN POSITION AGAINST DISPLACEMENT IN TWO DIRECTIONS, AND A SUBSTANTIALLY FIXED-LENGTH, REINFORCING CORD EMBEDDED IN SAID TAPE BENEATH THE INTERLOCKING ELEMENTS, EXTENDING LONGITUDINALLY THROUGH SAID TAPE ADJACENT THE SAID EDGE, EACH HEAD HAVING A CHAMFERED SURFACE BEYOND SAID EDGE OF THE TAPE, THE TAPE BEING OF THERMOPLASTIC MATERIAL AND HAVING SAID EDGE OF THE TAPE LONGER THAN THE OPPOSITE LONGITUDINAL EDGE WITH THE RELATIVE DIFFERENCE IN LENGTHS BETWEEN THE TWO EDGES DISPERSED UNIFORMLY OVER THE LENGTH OF THE TAPE, SAID STRINGERS BEING ASSEMBLED TO FORM SAID SUPPORT WITH SHORTER EDGES OF THE STRINGERS IN CONFRONTING RELATION. 